The invention relates to digital data recording medium, AV apparatus, and AV system which can easily control the recording or dubbing of a digital signal which is supplied from, for example, a television station or a digital VCR.
The invention also relates to a recording medium and a recording and reproducing apparatus which inhibits or restricts the recording (dubbing) and reproduction of a digital signal in order to protect its copyright.
In a digital recording and reproducing apparatus, for example, a digital VCR, there is hardly any deterioration of picture quality or sound quality during a dubbing (i.e., copying) process. Therefore, it is necessary to inhibit or restrict the dubbing or reproduction of certain data to protect a copyright. When an analog signal is input, converted to a digital signal and recorded, copyright protective information is superimposed in a vertical blanking period (V blanking period) of the analog signal to inhibit or restrict the dubbing of the digital signal.
In a pre-recorded tape for a conventional analog VCR, in order to protect the copyright, a copyright protective signal formed of a plurality of pairs, each comprising a sync pulse and a positive pulse, is superimposed in the V blanking period of the television signal. An Automatic Gain Control (AGC) of the recording section of a VCR is "confused" by such a signal, so that the dubbing cannot be performed. That is, in case of illegally copying a pre-recorded tape, the dubbed tape is copied so that it is unreproducible. Thus, the copyright is protected.
A VCR for an image compression system has been studied and developed. A digital VCR in which video and audio data are encoded, recorded and reproduced, such as the D1 component system, D2 composite system, and the like for business or professional use have been proposed with copyright protection. For instance, in an industrial-use digital VCR, signals such as the V blanking period and the horizontal blanking period (H blanking period) which do not represent image information are not recorded. Namely, only signals in the useful image portion are extracted, compressed, and recorded. Upon reproduction, such image data is subjected to processes opposite to those executed upon recording, so that the V and H blanking periods which were not recorded are added to the processed image data and the resultant data is output as a composite video signal.
FIG. 10 is a diagram showing an AV (audio/video) system for dubbing a pre-recorded tape onto a blank tape using digital VCRs. In FIG. 10, when a pre-recorded tape 101 is reproduced by a VCR 102, digital data, such as AV data, recorded on tape 101 is supplied through a cable 103 to a VCR in which a blank tape 105 is loaded. Tape 101, recorded by a compression system used in professional digital VCRs, as mentioned above, only contain data of the useful image portion; therefore, since there is no V blanking period, the analog VCR copyright protection techniques are not adequate when recording or dubbing signals using the digital VCR.